Method of making heat exchange units



Oct. 13, 1942.

R. H. MCKIBBEN' ET AL 2,298,895

METHOD OF MAKING HEAT EXCHANGE UNITS Filed Feb. 28, 1942 2 Sheets-Sheet l Figz.

lhvje ntor-s David M Dar-bf by W044? 6.17M Their" Attorney Oct. 13 1942. R. H. MCKIBBEN ETAL 2,298,395

METHOD OF MAKING HEAT EXCHAfiGE UNITS Filed Feb. 28, 1942 2 Shets-Sheet 2 Inventors: v

Poy HJ I Kibloen, David PLDarC. w mu fidw w Their Attorney.

Patented Get. 13, 1942 Roy 11. McKibben, Bloomfield, and David M. Dart, Essex Fells, N. 1., assignors to General Electric Company, a corporation of New York Application February 28, 1942, Serial No. 432,814

9 Claims. (cue-151.9 I

This invention relates to heat exchange units of the type having self-draining tubes, and particularly to a method of constructing such units.

Finned tube heat exchange units are frequently built by providing a plurality of parallel tubes and stacking a plurality-of fins on the tubes, each fin extending across all the tubes and having suitable openings to receive the tubes. For manufacturing purposes it is desirable that all the fins be of identical construction so that they may be made with the same tools and so that when they are stacked on the tubes they extend at right angles to the axes of the tubes and form a rectangular unit. In steam'heating systems,

for example, it is desirable that the several tubes of the heat exchange unit or radiator be pitched at an angle from the horizontal so' that water condensed in the tubes cannot collect therein, thus preventing a reduction of the effectiveheat transfer surface and also avoiding the possibility of damage due to freezing of trapped water during winter weather. The tubes of the out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of this invention reference may be hadto the accompanying drawings in which Fig. 1 is a front elevation view of a bank of finned tubes formed in an initial step of the invention; Fig. 2 is an end view of the bank of fins shown in Fig. 1; Fig. 3 is a front elevation view of a complete heat transfer unit constructed' in accordance with the invention; Figs. 4 and 5 are views similar to Figs. 1 and 3 illustrating steps in a'modification of the invention; Fig. 6 is a top plan view of the heat transfer.

- unit shown in Fig. 5; and Figs. 7 and 8 are diagrammatic views of a further modification of the invention.

Briefly, the heat transfer unit disclosed in the drawings is constructed by first stacking a plurality of identical fins in spaced relation on a plurality of parallel tubes, the fins being arranged at right angles to the tubes. The fins of the bank of tubes thus formed are then cut lonusual rectangular bank of tubes may be given the desired pitch by slanting the unit. However, in many installations it is not practical to have an entire unit including the steam and exhaust headers arranged at an angle to the vertical. Furthermore, if the unit is arranged in the usual rectangular duct as employed in forced air circulating systems, it'is desirable that the duct be arranged with its sides vertical, and consequently, if the unit is tilted at an angle, it becomes necessary to fill the triangular spaces thus formed in order tominimize the bypassing of air around the fins. Another method of constructing the heat exchange unit so that tubes have the required pitch is tovary progressively the positions of openings in the fins and to stack the fins on the unit at the desired angle so that the fins provide a rectangular outline and the tubes extend at an angle through the bank of fins. This construction, however, is objectionable since it involves the stacking *of the fins at an.

angle other than a right angle and also requires differences in locations of the holes in the several .one plate toward the other.; The cut edges of the two sections of the bank oftubes are arranged at the top and bottom respectively of the completed unit sov that the outline of the completed unit presents a minimum rectangle. If it is desired to eliminate entirely the triangular spaces between the fins and the end-plates, the

bank of tubes as originally constructed maybe canted or deformed so that it'has an outline in the form of a parallelogram the sldesof which are pitched from the horizontalat an angle cor- 1 responding to the desired pitch of the tubes. The bank of tubes may then be dipped in solder fins. Accordingly, it'is an'obiect of this invention to provide an improved method for constructing a heat transfer unit of the self-draining type such that identical fins may be employed in the construction and so that the completedunit is rectangular in outline.

Further objects and advantages of this invention will become apparent as the following description' proceeds, and the features of novelty or otherwise suitably retained in its new form and a cut made between two of the tubesat right angles to the fins. when the two portions thus formed are interchanged and built into a complete unit the outline of the finned structure I will be rectangulanwith the tubes pitched at the desired angle.

Referring now to-Flgs. 1 and 2, a plurality of straight tubes 10- is arrangedinparallel-spaced relationship a plurality offins il having holes punched therein correspondingto the powhich characterize this invention will be pointed sitions oi the tubesis'stacked on the tubes at tubes and at an angle equal to the desired pitch of the tubes in the completed self-draining unit. In the bank illustrated in the drawings the fins are out along a line l2, the cuts of the individual fins being at right angles to the longitudinal edges of the fins as indicated on the end fin shown in Fig. 2. An inlet header l3 having an inlet connection I31: and an outlet header I4 having an outlet connection Ha are then provided as shown in Fig. 3 and also end-platesror boxes I 5 and I6 which enclose the headers l3 and M, respectively. The headers, as well as the end-plates, may serve as supports. The positions of two portions of the bank of tubes formed as shown in Fig. 1 are then interchanged, and the separated portions are connected between the headers l3 and I4 and the plates l5 and It with the cut edges of the banks at the top and bottom respectively of the headers, the cut edges of the fins along the line I! being arranged at right angles to the axes of the headers so that the left-hand ends of the tubes which communicate with the header I3 are higher than the right-hand ends of the tubes which communicate with the header H. The end-plates Ii and it are, of course, provided with suitable openings to allow the tubes to pass therethrough, and the entire assembly presents a rectangular appearance. The spaces between the end fins and the plates l5 and it are relatively small and do not decrease the effective heat transfer area, while the fins extend completely across the spaces at the top and bottom of the unit so that there is a minimum open face area: In Fig.3 the two portions of the bank of Fig. 1 have been shown mounted at the top and bottom of a unit the middle portion of which comprises a single bank identical with the bank shown in Fig. 1, but whichhas not been cut; the middle bank being mounted with its tubes parallel to the tubeslof the top and bottom-banks or portions. The triangular spaces between the end fins of the middle bank and the plates II and it are relatively small, and furthermore, the ends of the tubes v extend through these spaces so that the spaces do not, in fact, present a completely open portion of the face area. V

It is thus clear that a self-draining unit of any desired size may be built up by providing two top and bottom bank portions in the manner described in connection with Figs. 1 and 2 by inserting therebetween any suitable number of intermediate banks of rectangular form like that of the complete unit'of Fig. 1. when a-smaller -unlt is desired it is, of'course, unnecessary to provide the intermediate ormiddle bank of tubes. Should it be desired\to eliminate entirely the small triangular spaces between the end-plates II and I. an additionalstep may be employed as illustrated in Figs. 4 and 5. In Fig. 4 the bank of tubes has been shown with the upper portion of the bank of tubes pressed or canted slightly to the left, as indicated by the position of the tube ends with respect toa vertical dotted line 8, so that a, parallelogram is formed the 1| angles of which differ from a right angle by the amount of pitch desired in the tubes of the finished heat transfer unit. The bank of tubes as shown in Fig. 4 is preferably dipped in solder or 5 otherwise suitably retained as a rigid unit after it has been formed as shown in Fig. 4, and the fins between two of the tubes are then out along a line such as indicated at H, the cut being at right angles to the fins and, therefore, at the desired angle of pitch with respect to the tubes. After the two portions of the bank have been formed in this manner they may be placed in a complete heat transfer unit as indicated in Fig. 5. The heat transfer unit of Fig. 5 comprises frontand rear sections as clearly shown in Fig. 6, both sections having their tubes slanted at the desired pitch. In Fig.5, for purposes of clear.- ness, no attempt has been made to illustrate the fins on the rear bank. The heat transfer bank comprises end-plates or boxes l8 and I9, and the heat transfer units formed as shown in Fig. 4 are placed at the top and bottom respectively with the fins parallel to the upright sides of the plates I8 and I9 and the cut edges at right angles to the plates. The left and right ends of the tubes are then belled as indicated at 20 and 2|, respectively, and an inlet header 22 having an inlet connection 22a is connected to the several left-hand ends of the tubes by suitable connectors 23. The right-hand ends of the tubes of the front bank are connected by end-turns 24 to the rear bank as clearly shown in Fig. 6, the rear bank having its tubes pitched in the opposite direction from the front bank so that there is a continuous slope from the left-hand tube of the front bank to the left-hand tube of the rear bank. The left-hand ends of the rear bank are connected to an outlet header or manifold 25. The central section of the heat transfer surface shown in Fig. 5 is a complete bank con-. structed as shown in Fig. 4, this middle section being inserted between the two out sections in the same manner as the middle section of the heat transfer unit shown in Fig. 3, it being obsmaller unit is required or that further sections may be added if it is desired to form a larger unit.

Figs. 7 and 8 illustrate a further modification f the invention whereby a single bank of tubes is cut and rearranged to have one set of tubes pitched toward one end of the bank and another set pitched toward the other end of the bank, the tubes being connected by return bends so that each tube comprises a continuous hairpin conduit. In the illustrated construction, which is somewhat diagrammatic, the three central tubes are separated from the original rectangular bank by two outs along lines 20 and 21 iongitudinally of the tubes andat the desired angle of pitch. The two outer portions of the bank formed by the two cuts and indicated at 28 and 2! correspond to the two sections formed in Fig.

1 and may be interchanged and assembled in the g same manner as the sections in Fig. 1 to provide a.rectangular-bank, as shown in the lower portion of Fig. 8. The separated central portion indicated at Il may then be inverted and placed on top of this bank so that the tubes thereof are pitched in the opposite direction to that of the tubes in the bank comprising sections 28 and II, the angle between the tubes in the lower bank andthoseintheupperbeingtwicetheangleof pitch. Aninletheaderllmaybeconnectedto the'unoer set of tubes 8. and an outlet header vious that this section is not necessary if a 32 to the lower set that steam or other fluid may pass from the inlet header through one set of tubes and through return bends it and the other set f tubes to the outlet header. This provides'a simple arrangement making it possible to locate both headers at the same end of a unit having a bank of flnned tubes which may be included within a minimum rectangle.

From the foregoing it is apparent that this invention provides an improved and easily aptubes of the self-draining type and that this bank provides the desired rectangular outline required for. installation particularly in forced air circulating ducts of rectangular cross-section and that a minimum rectangle is secured.

While this invention has been described in connection with a particular'form of self-draining unit, other applications will readily be apparent to those skilled in the art. It is, therefore, not desired to limit this invention to the particular construction shown and described, and it is intended in the appended claims to cover all modiflcations within the spirit and scope of the invention. 1 i

What we claim as new and desire to secure by letters Patent of the United States is:

l. The method of constructing a heat transfer unit including a bank of finned tubes of the selfdraining type which comprises providing a bank of finned tubes having-the form of a parallelogram and comprising a plurality of parallel straight tubes and substantially parallel elongated fins mounted on said tubes transversely thereof, cutting said bank of finned tubes between two of said tubes longitudinally at an angle equal to the desiredwpitch of the tubes of the completed unit to form two separate portions of said bank, and interchanging the relative positions of said portions and assembling said portions to provide the top and bottom sections of a finished bank of tubes having the desired pitch for drainage and which bank may be included within a minimum rectangle.

2. The method ofconstructing a heat transfer unit including a bank of finned tubes of the selfdrg type which comprises providing'a bank of ed tubes having the form of a parallelogram and comprising a plurality of parallel straight tubes and substantially parallel elongated iins mounted on said tubes transversely thereof, cutting said bank of finned tubesbetween two of said tubes longitudinally at an angle equal to the desired pitch of the tubes of the compieted unit to form two separate portions of said 10 plied method for constructing a bank of finned of the tubes of the completed unit to form two separate portions of said bank, and interchanging the relative positions of said portions and assembling said portions to provide a finished bank of tubes having the desired pitch for drainage and which bank may be included within a minimum rectangle.

4. The method of constructing a heat transfer unit including a bank of finned tubes of the selfdraining type which comprises providing 8. rectangular bank of finned tubes comprising a plurality of parallel straight tubes and parallel elongated flns mounted on said tubes at right angles to the axes thereof, cutting said rectangular bank of finned tubes between two of said tubes longitudinally at an angle equal to the desired pitch of the tubes of the completed unit to form two separate portions of said bank,'interchanging the relative positions of said portions, and assembling said portions between two opposite parallel elongated supporting members with thecut sides of said portions at right angles to the longitudinal gated fins'mounted on said tubes at right angles bank, interchanging the relative positions of said portions, and assembling said portions between two opposite parallel elongated supporting membars with the cut sidesof said portions at right angles to the longitudinal axes of-said supporting members to provide the top and bottom sections of a had whereby said tubes are pitched from one of said members to the other at the desired angle for drainage and whereby the finished herds of tubes may be included within a um rectangle.

3.. The method of constructing a heat transfer unit including a m: oftflnned tubes of the selfdraining type which comprises providing a rectangular bank of finned \tubes comprising a plurality of parallel straight tubes and parallel elongated fins mounted on said tubes at right angles to the axes thereof, cutting said, rectangular bank of finned tubes between two of said tubes longito the axes thereof, deforming said bank so that it forms a parallelogram the angles of which diifer from right angles by the desired angle of pitch of the tubes, retainingsaid bank in its deformed position and cutting said bank of finned tubes between-two of said tubes longitudinally at an angle equal to the desired pitch of the tubes of the completed unit to form two separate portions of said bank, and interchanging the relative positions of said portions and assembling said portions to provide a finished bank of tubes having the desired pitch for drainage and which bankmaybe included within a minimum rectangle.

6. The method of constructing a heat transfer unit including a bank of finned tubes of the selfdraining type which comprises providing a rectangular bank of iinned tubes comprising a pinrality of parallel straight tubes and parallelelongated finsmounted on said tubes at right angles to the axes thereof, deforming said bank so that it forms a parallelogram the angles of which diifer from right angles by the desired angle of pitch of the tubes, retaining said bank in its deformed position and cutting said bank of finned tubes between two of said tubes longitudinally at an angle equal to the desired pitch of the tubes of the completed unit to form two separate portions oi said :1. i interchanging the relative positions oi said portions, and assembling said portions between two opposite parallel elongated. sup= porting members with said parallel to said rrierhloersv whereby said tubes are pitched from one of said members to the other at the desired angle for drainage and whereby the d t ll: of tubes may be included within a minimum rectangle. 7. The method of constructinga heat transfer unit including a bank of iinned tubes of the selfdraining type which comprises providing a pina plurality of parallel straight tubes and parallel tudinally at an angle equal to the desired pitch l5 elongated fins mounted on said tu s at right angles to the axes thereof, cutting one of said banks of finned tubes between two oi! the tubes thereof longitudinally at an angle equal to the desired pitch oi. the tubes of the completed unit to'torm two separate portions of said one bank,

of the tubes of said banks at said desired angle of pitch from one of said plates to the other. whereby the finished bank of tubes may be included within a minimum rectangle.

8, The method of constructing a heat transfer unit including a bank oi finned tubes of the selfdraining type which comprises providing a rectangular bank of finned tubes comprising aplurality of parallel straight tubes and parallel elongated fins mounted on said tubes at right angles to the axes thereof, cutting said rectangular bank of finned tubes between two of said tubes longitudinally at an angle equal to the desired pitch of the tubes of the completed unit to form two separate portions of said bank, interchanging the relative positions of said portions and assembling said portions between two parallel tube sheets with the cut sides of said portions at the top and bottom of said tube sheets and at right angles to the planes of said tube sheets, arranging headers at the ends of said tubes outside said tube sheets arid connecting said tubes in communication with said headers, whereby the tubes are pitched from one of said headers to the other at the desired angle for drainage, and whereby the cut edges of said fins are substantially flush with the tops and bottoms respectively of said tube sheets.

9. The method of constructing a heat transfer unit including a bank of finned tubes of the selfdraining type which comprises providing an elongated bank of finned tubes comprising a plurality of parallel straight tubes and parallel elongated fins mounted on said tubes at right angles to the axes thereof, removing a group of tubes from said bank by cutting said fins longitudinally of said tubes at an angle. equal tothe desired pitch oi the tubes of the completed unit and along lines on either side of said group of tubes whereby said bank is divided into three portions, interchanging the relative positions of said portions and assembling said portions with the cut sides 01' two 01' said portions along the outer sides of the completed unit and parallel to one another and with the other portion arranged between said two portions, whereby the tubes in said group oi tubes are pitched at the desired angle in one direction and the tubes in the other portions of said bank are pitched at the desired angle in the other direction, and connecting the ends of said tubes byreturn bends to provide continuous hairpin conduits pitched downwardly throughout their length, the completed bank being thereby assembled so that it may be included within a minimum rectangle.

ROY H. McKIBBEN. DAVID M. DART. 

